The present invention relates generally to pulse generators and is more particularly concerned with a new and improved pulse generator having an asymmetrical multi-pole magnet suited for use with a Hall effect pickup and with a magnetizing head particularly adapted to producing such an asymmetrical magnet.
Heretofore rotary pulse generators have been constructed with a magnetic readout head incorporating a Hall sensor and with a magnetic rotor cooperating with the readout head for applying an alternating magnetic field to the Hall sensor. Typical of such devices are the rotary pulse generators described in U.S. Pat. No. 3,742,243. In that patent one embodiment includes a rotor comprised of a pair of spaced coaxial ring magnets providing a plurality of substantially symmetrical poles of alternating magnetic polarity arranged for producing an alternating magnetic field within an annular air gap between the rings. per cent magnetic rings produce a salient magnetic field of dual polarity, i.e. in the positive and negative regions, resulting from the symmetrical multi-pole configuration of the magnetic ring construction. Substantially equally spaced electrical signals are generated within the Hall sensor as the rotor moves through a predetermined increment of angular displacement. In practice, it has been found that most rotary pulse generators are designed with a duty cycle operative within only the positive region of the magnetic curve so that the operate and release points of the Hall sensor switch most commonly use a maximum of only 50 percent of the total duty cycle of each pole pair of the magnets during their rotation. In actual practice the duty cycle obtained is limited to substantially less than 50 per cent and is generally in the range of thirty to 45 per cent of the magnetic flux curve for each pole pair. Accordingly, it is an object of the present invention to provide a new and improved pulse generator of the type described that utilizes a salient magnetic field of single polarity thereby extending the utility of the magnet and increasing the effective duty cycle thereof.
Another object of the present invention is to provide a multi-pole magnet having a plurality of symmetrically spaced pole pairs wherein the magnetic pole of one polarity occupies a substantially asymmetrical relationship to the pole of the opposite polarity to provide a salient magnetic field having an effective single polarity. Included in this object is the provision for the use of such a magnet within a Hall effect pulse generator.
Still another object of the present invention is to provide a new and improved asymmetrical multi-pole magnet having an extended duty cycle and therefore increased utility within a greater variety of applications.
A further object of the present invention is to provide a new and improved Hall effect pulse generator including an asymmetrical multi-pole magnet capable of providing a more perpendicular flux field capable of tolerating axial displacement of the magnet assembly with negligible effect on the duty cycle.
A still further object of the present invention is to provide a new and improved magnetizing head capable of rapidly and effectively producing an asymmetrical multipole magnet of the type described.
Other objects will be in part obvious and in part pointed out in more detail hereinafter.
These and related objects are accomplished in accordance with the present invention by providing a pulse generator comprising a magnetic field generator means and a Hall sensor operative for generating an electrical signal upon the application of a magnetic field thereto. The Hall sensor and magnetic field generator means are mounted for relative movement for the generation of a train of electrical signals in response to relative displacement therebetween. The magnetic field generator means includes an asymmetrical multi-pole magnet having a plurality of symmetrically spaced pole pairs. Each pole pair includes a magnetic pole of predominant polarity occupying a substantially greater area than the pole of opposite polarity with the predominant pole being sufficiently strong to provide a salient magnetic field of essentially single polarity. The asymmetrical magnet is formed of ceramic material and is magnetized using a magnetizing head comprising a cylindrical metal core having one end comprised of a symmetrical array of axially extending segments of substantially equal size, a winding fully circumscribing alternate segments and electrically insulated therefrom with the last turn of the winding on each alternate core segment being substantially flush with the one end of the core and an encasement protectively enclosing the winding and the segments while permitting exposure of the segments at the one end.
A better understanding of the invention will be obtained from the following detailed description and the accompanying drawing which set forth an illustrative embodiment indicative of the way in which the principles of the invention are employed.